13 papers
Boron-doped diamond
Vassiliki Katsika-Tsigourakou
Boron-doped diamond undergoes an insulator-metal transition at some critical value (around 2.21 at %) of the dopand concentration. Here, we report a simple method for the calculati…
Multiphased alkali halide mixed crystals: The conductivity activation energy
Vassiliki Katsika-Tsigourakou, Chrysoleon Symeonidis
The preparation of mixed crystals of NaBr and KBr from melt as well as their physical characterization have been reported. Electrical measurements were carried out at various tempe…
The dielectric constant of Na_{0.4}K_{0.6}Br and its large temperature variation
V. Katsika-Tsigourakou, P. Bekris
Since polycrystals of alkali halides are highly useful as components in optical devices, a number of mixed crystals of NaBr and KBr have been prepared from melt by other workers. A…
(NaCl)_x(KCl)_{y-x}(KBr)_{1-y} single crystals: study of the ac conductivity activation energy
Vassiliki Katsika-Tsigourakou
Ac electrical measurements have been reported for alkali halide mixed crystals that were melt grown from NaCl, KCl and KBr starting materials. They showed a nonlinear variation of…
Calculation of the bulk modulus of mixed ionic crystal NH_4Cl_{1-x}Br_x
Vassiliki Katsika-Tsigourakou
The ammonium halides present an interesting system for study in view of their polymorphism and the possible internal rotation of the ammonium ion. The static properties of the mixe…
Study of the composition dependence of the ionic conductivity of LiH_{x}D_{1-x} alloys
Vassiliki Katsika-Tsigourakou
Recent observations have shown that at a certain composition of solid solutions AgClBr, AgCl-CdCl, AgBr-CdBr, of ionic crystals, the electrical conductivity exh…
A remark on the negative activation volume for defects in solids
Vassiliki Katsika-Tsigourakou
The evolution of the aging process of glassy materials quenched from temperatures above their glass transition temperature , when plotting the relaxed enthalpy versus the decr…
Relaxed enthalpy and volume during physical aging: Their interrelation
Vassiliki Katsika-Tsigourakou, Georgios E. Zardas
Several papers have recently presented results of measurements of physical aging by studying the behavior of glassy materials quenched from temperatures above their glass transitio…
On the compressibility of the transition-metal carbides and nitrides alloys Zr_xNb_{1-x}C and Zr_xNb_{1-x}N
Vassiliki Katsika-Tsigourakou
The 4d-transition-metals carbides (ZrC, NbC) and nitrides (ZrN, NbN) in the rocksalt structure, as well as their ternary alloys, have been recently studied by means of a first-prin…
Defect entropies and enthalpies in Barium Fluoride
Vassiliki Katsika-Tsigourakou, Efthimios S. Skordas
Various experimental techniques, have revealed that the predominant intrinsic point defects in BaF are anion Frenkel defects. Their formation enthalpy and entropy as well as th…
A tentative model for estimating the compressibility of rock-salt AgCl_{x}Br_{1-x} alloys
V. Katsika-Tsigourakou, E. S. Skordas
Ab initio detailed calculations of the elastic properties of AgCl_{x}Br_{1-x} alloys recently appeared using density-functional perturbation theory and employing the virtual crysta…
Heterodiffusion coefficients in α-iron
V. Katsika-Tsigourakou, E. S. Skordas
The diffusion of tungsten in α-iron is important for the application of ferritic-iron alloys to thermal power plants. These data, over a wide temperature range across the Curie tem…
Estimation of the effects of Y and Zn atoms on the elastic properties of Mg solid solution
Vassiliki Katsika-Tsigourakou
Mg-based alloys have recently attracted major interest in view of their potential applications in the aerospace, aircraft and automotive industries. Here, we show that the effects…